If you are not invested in a system, at this point in time I would highly recommend looking into the canon system. It pains me to say it but nikon has some real quality control issues going on and it is not fun to deal with if you are on receiving end of it. The canon 6D can be a very good choice for most people wanting FF. It has some down sides like a lower/slower performing AF system and single card slot but that is pretty much the major differences. If you read the lens rentals dear santa letter, you will get an amazing sense of where things are with each company at this time. If you have your heart set on nikon wait it out 6 months to a year and maybe nikon can get the d600 issue solved but if it is like the d800 LF issue, you will still be playing a game of luck.